Method and apparatus for measuring slurry concentration and velocity distribution in a slurry pipeline

ABSTRACT

A method and apparatus for measuring the slurry concentration and velocity distribution in a pipeline wherein a first probe is used to determine the velocity at a predetermined position in the pipeline and a sample probe is then moved to the position and sampling rate adjusted until the velocity response to the two probes are equal. The local value of the velocity is obtained by dividing volume per unit of time of the sample by the crosssectional area of the probe while the slurry concentration and particle size distribution are obtained by analysis.

United States Patent 1 [111 3,729,987 Chao et al. 51 May 1, 1973 METHODAND APPARATUS FOR FOREIGN PATENTS OR APPLICATIONS MEASURING SLURRYCONCENTRATION AND VELOCITY DISTRIBUTION IN A SLURRY PIPELINE Inventors:Junn-Ling Chao, Pasadena, Calif.; Moye Wicks, III; Thomas W. Pounds,both of Houston, Tex.

Assignee: Shell Oil Company, Houston, Tex.

Filed: Sept. 17, 1971 Appl. No.: 181,488

21 L147 4/1968 U.S.S.R. ..73/6l R Primary Examiner-Louis R. PrinceAssistant Examiner-1oseph W. Roskos Attorney-Theodore E. Bieber et al.

[5 7] ABSTRACT A method and apparatus for measuring the slurryconcentration and velocity distribution in a pipeline wherein a firstprobe is used to determine the velocity at a predetermined position inthe pipeline and a sample probe is then moved to the position andsampling [5 2] US. Cl. ..73/6l R, 73/212 rat adjusted until the velocityresponse to the two B Cl MGOln 15/06 probes are equal. The local valueof the velocity is ob- [58] Field Of Search ..73/6I R, 212 tained by i ivolume per i f i f h ple by the cross-sectional area of the probe whilethe [56] References C'ted slurry concentration and particle sizedistribution are UNITED STATES PATENTS Qbtained by analysis- 3,543,565[2/1970 De Koning et a1. ..73/6l R 6 Claims, 1 Drawing Figure ,5 1 5 /7I8 1 iBR/DGEI INULLMEIEQI i /OLTMETE/E 72 I 3 c 'f Lmfiwm 34 m j H F W i31 32 33 X 1 L 27 20 1 1' I l 3 I jam/36E] [NULLMETER] u OLTMETER] THREEWAY i I) Hm SOURCE OF VAL VE PRESSURE METHOD AND APPARATUS FOR MEASURINGSLURRY CONCENTRATION AND VELOCITY DISTRIBUTION IN A SLURRY PIPELINEBACKGROUND OF THE INVENTION In a slurry pipeline, it is desirable toknow both the velocity profile and the slurry concentration at variouspoints across the pipeline. This information is required in order thatthe operation of the pipeline may be maintained under conditions thatinsure that the slurry l remains in suspension. In slurry pipelines, ifsteps are not taken to maintain the proper velocity distribution acrossthe pipeline, it is possible for the solids to concentrate and plug thepipeline. When this occurs it is of course necessary to shut down thepipeline and reestablish the solid material in suspension to form aslurry.

Normally the slurry concentration is measured for the bulk of thepipeline and no accurate indication is obtained of the exact slurryconcentration at particular points across the pipeline. While thesemeasurements are useful, it is impossible to tell the exact conditionsexisting in the pipelines from such measurements.

BRIEF DESCRIPTION OF THE INVENTION The present invention solves theabove problems by providing a velocity profile of the pipeline acrossthe diameter of the pipeline. In addition, the slurry concentration ismeasured at each point at which a velocity measurement is made. Thus oneobtains a complete measurement of both the velocity profile and theslurry concentration across the diameter of the pipeline.

The above measurements are obtained by means ofa velocity probe which ismoved into a position in the pipeline for making a velocity measurement.After the velocity measurement is made, the probe is retracted and asampling probe moved into the position formerly occupied by the velocityprobe. The flow through the slurry sampling probe is controlled toobtain the same velocity as was previously measured by the velocityprobe. Once the isokinetic condition is established the time required toobtain a certain volume of sample can be measured and the velocitycalculated while the slurry concentration for the particular point inthe pipeline can be obtained from an analysis of the collected sample.The two probes can be moved to obtain a complete survey across adiameter of the pipeline.

BRIEF DESCRIPTION OF THE DRAWING The invention will be more easilyunderstood from the following description of the preferred embodimentwhen taken in conjunction with the attached drawing showing theinvention installed in a pipeline.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the encloseddrawing, there is shown the invention applied to a slurry pipeline 10.The velocity measuring probe 1] is mounted so that it may be extendedinto the pipeline as shown or retracted to a position indicated by thedotted outline 12. When retracted, the probe is positioned in a recess13 formed in the wall of the pipeline. The probe may be any type ofvelocity-measuring device but is preferably a thermistor whoseresistivity changes in response to the cooling effect of the slurryflowing in the pipeline.

The velocity probe is coupled by lead 15 to a bridge circuit 16 whoseunbalance is measured by nullmeter 17. The nullmeter 17 balances thebridge and supplies a signal related thereto to a voltmeter 18. Thevoltmeter displays the magnitude of the unbalanced bridge signal.

The sampling probe 21 is mounted diametrically opposite the velocityprobe and also provided with a means by which it may be moved into thepipeline to a dotted position 20. Both the sampling probe and thevelocity measuring probe should be provided with sufficient movement sothat they can completely traverse the pipeline to measure the velocityand sample the slurry flow at all positions. When the sampling probe isretracted, it rests in a recess 22 formed in the wall of the pipeline. Amovable wall portion 23 is provided so that the wall of the pipelinewill have a substantially smooth surface when the probe is extended intothe pipeline.

The sampling probe is connected by a line 24 to a three-way valve 25that is designed to couple the sampling probe either to a testing vessel26 or to a collecting vessel 27. The testing vessel 26 is provided witha velocity measuring probe 30 which is substantially identical in itsresponse characteristics to the velocity probe 11. The slurry sample isdirected onto the velocity measuring probe 30 and the slurry flow isthen adjusted until it exactly equals the flow in the pipeline. Thevelocity measuring probe 30 is coupled to a bridge circuit 31 whoseoutput is supplied to a nullmeter 32 which in turn is coupled to avoltmeter 33. The voltmeter 33 displays a signal related to theunbalance of the bridge which signal is also supplied by a lead 34 tothe voltmeter 18.

The flow through the sampling probe is controlled by varying thepressure within the testing vessel and the collecting vessels. Thepressure may be supplied from any source of pressure such as acompressed air source by means of a control valve 40 and a line 41connecting with the testing vessel 26 and a line 42 connecting with thecollecting vessel 27. The control valve may be controlled by the signalfrom the voltmeter 33 so that the flow through the sampling probe is atthe same velocity as previously measured by the velocity probe 11 at thesame position in the pipeline. Also it is possible to supply the signalfrom the voltmeter 18 as a reference signal to the voltmeter 33 so thatthe voltmeter 33 can adjust the control valve to obtain the propervelocity through the sampling probe. When isokinetic conditions areestablished the signals from the two voltmeters will be equal.

In operation, the velocity probe 11 is first positioned at a desiredlocation in the pipeline and a velocity measurement made. The signalrepresenting this velocity measurement is then supplied as a referencesignal to the voltmeter 33. The velocity probe is retracted into therecess in the sidewall of the pipeline and the sampling probe extendeduntil it occupies the position for merly occupied by the velocity probe.The flow through the sampling probe is then adjusted by varying thepressure in the testing vessel 26 until the signal from the voltmeter 33matches the signal from the reference. signal from voltmeter 18. Whenthe two signals match it indicates that the velocity in the samplingprobe is the same as the velocity in the pipeline and isokineticconditions have been established. The three-way valve 25 is thenpositioned to divert the flow from the sampling probe into thecollecting vessel 27. A measured quantity of the slurry is collectedwhile measuring the time required to collect the sample. Knowing thevolume collected and the time, one can determine an accurate rate offlow in the pipeline. Likewise, one can determine the concentration ofthe slurry by an analysis of the sample collected in the vessel 27.

The rate of flow can be determined on a simple computer or a specialdividing circuit can be provided for dividing the volume by time. Eitherof these steps can be carried out by one skilled in the art or aconventional dividing circuit using an operational amplifier may beused. The volume of the sample and time may be measured by commerciallyavailable equipment. A second operational amplifier can be used todivide the flow rate by the cross-section of the probe to obtain thevelocity. While the slurry concentration can be obtained by a physicalanalysis of the sample, it can also be obtained automatically. Theconcentration is related to density which is proportional weight dividedby volume. The weighing of the sample can be done by weigh cells orother devices that supply electrical signals related to weight. Theconcentration can then be obtained using a commercial dividing circuit.

The above procedure is repeated for a number of points across thepipeline to obtain an accurate profile of the rate of flow and theslurry concentration in the pipeline. Once sufficient data is obtained,one can plot the profile of the flow rate and the slurry concentrationand determine what corrective steps, if any, are required.

The system can be further modified to fully automate both thepositioning and retracting of the velocity and sampling probes as wellas the matching of the voltmeter signals. Of course, for laboratory usea more simplified system is possible wherein the operator manuallymanipulates the control valve 40 and visually measures the collection ofthe required volume while noting the time required.

We claim as our invention:

1. A method for determining the velocity profile and solidsconcentration profile in a slurry pipeline comprising:

measuring the velocity at a first position in the pipeline;

sampling by means of a sample probe the slurry in said pipeline at saidfirst position, while adjusting the sampling rate by discharging thesample from the sample probe onto a probe that is substantiallyidentical to the probe used to measure the velocity in the pipeline sothat the velocity in the sample probe equals the measured velocity atsaid first position;

collecting a known volume of sample while measuring the time required tocollect the known volume of sample; and

determining the velocity of slurry flow at said first position from saidmeasured volume and the crosssectional area of the sample probe.

2. An apparatus for measuring the velocity profile and slurryconcentration in a slurry pipeline, said apparatus comprising:

a first velocity measuring probe, said velocity measuring probe beindisposed to be extended into the pipeline and re racted to a positionbeyond the wall of the pipeline;

a first measuring circuit, said velocity probe being coupled to saidfirst measuring circuit;

a sampling probe, said sampling probe being disposed to be extended intothe pipeline and retracted to a position beyond the wall of thepipeline,

a testing vessel, said sampling probe communicating with said testingvessel;

a second velocity measuring probe, said second velocity measuring probebeing mounted in said testing vessel and disposed so that said sampleprobe discharges onto said second velocity measuring probe;

a second measuring circuit, said second velocity probe being coupled tosaid second measuring circuit;

flow control means disposed to control the flow through said samplingprobe whereby the signal from said second measuring circuit may bevaried to equal the signal from the first measuring circuit; and

a collecting vessel, said sampling probe communicating with saidcollecting vessel.

3. The apparatus of claim 1 wherein said first and second velocityprobes are thermistors.

4. The apparatus of claim 1 wherein said sampling probe communicateswith said testing and said collecting vessels through a three-way valve.

5. The apparatus of claim 1 wherein said velocity probe and saidsampling probe are mounted on diametrically opposite sides of saidpipeline.

6. The apparatus of claim 1 wherein said flow controlmeans comprisesmeans for controlling the pressure in said testing and said collectingvessels.

1. A method for determining the velocity profile and solidsconcentration profile in a slurry pipeline comprising: measuring thevelocity at a first position in the pipeline; sampling by means of asample probe the slurry in said pipeline at said first position, whileadjusting the sampling rate by discharging the sample from the sampleprobe onto a probe that is substantially identical to the probe used tomeasure the velocity in the pipeline so that the velocity in the sampleprobe equals the measured velocity at said first position; collecting aknown volume of sample while measuring the time required to collect theknown volume of sample; and determining the velocity of slurry flow atsaid first position from said measured volume and the cross-sectionalarea of the sample probe.
 2. An apparatus for measuring the velocityprofile and slurry concentration in a slurry pipeline, said apparatuscomprising: a first velocity measuring probe, said velocity measuringprobe being disposed to be extended into the pipeline and retracted to aposition beyond the wall of the pipeline; a first measuring circuit,said velocity probe being coupled to said first measuring circuit; asampling probe, said sampling probe being disposed to be extended intothe pipeline and retracted to a position beyond the wall of thepipeline, a testing vessel, said sampling probe communicating with saidtesting vessel; a second velocity measuring probe, said second velocitymeasuring probe being mounted in said testing vessel and disposed sothat said sample probe discharges onto said second velocity measuringprobe; a second measuring circuit, said second velocity probe beingcoupled to said second measuring circuit; flow control means disposed tocontrol the flow through said sampling probe whereby the signal fromsaid second measuring circuit may be varied to equal the signal from thefirst measuring circuit; and a collecting vessel, said sampling probecommunicating with said collecting vessel.
 3. The apparatus of claim 1wherein said first and second velocity probes are thermistors.
 4. Theapparatus of claim 1 wherein said sampling probe communicates with saidtesting and said collecting vessels through a three-way valve.
 5. Theapparatus of claim 1 wherein said vElocity probe and said sampling probeare mounted on diametrically opposite sides of said pipeline.
 6. Theapparatus of claim 1 wherein said flow control means comprises means forcontrolling the pressure in said testing and said collecting vessels.